In order to obtain good functioning of a de-stacker, it is essential that the feed device with which it is associated ensures proper presentation of the mail.
Several technical problems arise in the region of the de-stacker head.
Firstly, the incidence of damaged or torn articles should be minimized; in particular, the de-stacking of open mail in the nature of sheets folded into several flaps or small publicity or other brochures is especially subject to de-stacking problems, the conventional frictional anti-double-feed systems lead to creasing up or tearing of the mail items.
Secondly, the flow rate, i.e. the number of mail items treated per hour of operation should be maximized.
Thirdly, the incidence of multiple feeds occasioned by failure of mail items to separate should be minimized.
Fourthly, the dispersion in the frequency of injection into the sorting system should be optimized; more particularly, in the case of injection with spaces between mail items, it is necessary to take account of the repetition rate of the spaces between items (distance between trailing edge and leading edge) or the pitch (distance between leading edge and leading edge) and to respect a minimum spacing which is a value set by the performance of the sorting machine; in the case of injection with shingled items, it is necessary to take account of the repetition rate of the overlap value.
Moreover the known feeding devices are either of small capacity or compartmented, which makes loading the mail difficult and leads to a long loading time and thus to reduction in efficiency.